Observer-based control technique for a grid-connected DC/AC converter used in renewable energy applications

This paper presents sensorless techniques for a grid-connected voltage source inverter with an LCL-filter in order to improve the closed-loop control performance and reduce the overall cost of the converter through an observer-based control approach. The observability of the system is mathematically analyzed using the system state-space equations, and then two state observers are designed and the closed-loop performance of the observers is compared in detail. The observer-based controller is implemented on a grid-connected voltage source inverter. The experimental results demonstrate the feasibility of the proposed closed-loop control system and superior performance particularly in terms of noise susceptibility.